Copolymers of vinyl alkyl ethers and vinyl esters



United States Patent 3,141,866 COPOLYMERS OF VINYL ALKYL ETI-ERS AND VlNY L ESTERS Frank A. Stuart, Orinda, and Warren Lowe, San Francisco, Calif., assignors to California Research Corporation, San Francisco, Calif., a corporation of Delaware N0 Drawing. Filed Aug. 10, 1959, Ser. No. 832,440 3 Claims. (Cl. 260-805) This invention relates to superior new copolymers. More particularly, the invention is concerned with novel copolymers of vinyl alkyl ethers and alkyl esters having unusual thickening properties.

Copolymers are used as modifiers for Waxes, asphalts, resins, rubbers and synthetic plastics. They may also be used as gelling agents for liquid hydrocarbons.

In particular, copolymers are used to thicken and improve the viscosity-temperature characteristics of lubricating oils and greases. In such applications, the thickened lubricant compositions provide effective lubrication over a considerable temperature range. Thus, at high temperatures normally encountered in the usual operation of internal combustion engines a lubricant film of adequate thickness is provided While in the same engines the lubricant is sufficiently fluid to circulate freely at conventional low starting temperatures.

It has now been found that surprisingly effective thickeners are provided in the copolymers of (A) vinyl alkyl ether having from 2 to 6 carbon atoms in the alkyl group and (B) at least one ester of the class consisting of alkyl acrylates and alkyl methacrylates having from 4 to 12 carbon atoms in each of the alkyl groups, the total of carbon atoms in the alkyl group of (A) and the average alkyl group of (B) being from about 8 to about 12, the mol ratio of (A) to (B) being approximately 1:1 and the molecular weight of the copolymer being at least 50,000.

The copolymers of the invention as described above possess outstanding thickening properties compared to other closely related copolymers. In lubricating oil compositions in particular, the copolymer thickeners of the invention impart excellent viscosity-temperature properties as indicated by the unusually high viscosity index. The particular balance of the carbon atoms in the alkyl groups of the copolymers as well as the ratio of the spesemifina l. it? i. it...

in which R is an alkyl group of from 2 to 6 carbon atoms and R and R are alkyl groups of from 4 to 12 carbon atoms each, all of which may be the same or different from one another, R and R are members of the class consisting of hydrogen and methyl groups, and W, x and y being the relative occurrence of the (A) and (B) monomer units, as mentioned above, in which relationship w is equal to 1 while x and y are fractional numbers, the sum of which is equal to 1, the total occurrence of the monomer units in the formula being equivalent to a molecular weight of at least 50,000 for the total copolymer, the ratio of w to x-l-y being approximately 1: l and the total carbon atoms of wR and xR +yR being from about 8 to about 12.

Suitable unsaturated alkyl ethers within the above description include vinyl isobutyl ether, vinyl n-butyl ether, vinyl 2-ethylhexyl ether, etc. For present purposes, the

ice

vinyl alkyl ethers having 4 to 6 carbon atoms in the alkyl group are preferred.

Alkyl esters of methacrylic acid and acrylic acid in accordance with the above formula include n-octyl methacrylate, n-octadecyl acrylate, 2-ethylhexyl acrylate, Oxo decyl methacrylate, n-butyl methacrylate, etc. The alkyl methacrylates having 4 to 12 carbon atoms in the alkyl groups are presently preferred.

The copolymers are prepared by conventional bulk, solution or emulsion methods, in the presence of an addition-type polymerization initiator. Preferably, the copolymerization is elfected in an inert organic solvent, such as benzene, toluene, xylene or petroleum naphtha, in the presence of a free radical-liberating-type initiator such as a peroxy compound, for example, benzoyl peroxide, acetyl peroxide, tert. butyl hydroperoxide, di-tert. butyl peroxide, di-benzoyl peroxide, or di-tert. amyl peroxide, or an azo initiator such as 1,l-azodicyclohexane-carbonitrile or a,'-azodiisobutyronitrile, or a persulfate, such as potassium persulfate. The catalyst, or polymerization initiator, is employed in an amount of from about 0.1 to 10%, with a preferred range being from 0.10 to 2%. If desired, the catalyst can be added in increments as the reaction proceeds. Likewise, additional portions of the solvent can also be added from time to time in order to maintain the solution in a homogeneous condition. The temperature of copolymerization varies from about to 300 F., with the optimum temperature for any given preparation depending on the nature of the solvent, the concentration of monomers present in the solvent, the catalyst, and the duration of the reaction. Much the same conditions are employed when the copolymerization is effected in bulk rather than in the presence of an inert solvent.

The copolymers have molecular weight of at least about 50,000, as already mentioned. The molecular Weight may run as high as several million or more. Polymers having molecular weights of from about 200,000 to about 1,000,- 000 are preferred. The aforementioned molecular weights are based on standard viscosity determinations.

The following specific example illustrates the preparation of the copolymer of vinyl isobutyl ether, n-butyl acrylate and n-octyl acrylate.

Into a 2liter, 3-necked flask equipped with water condenser, addition, funnel, thermometer stirring unit and heating means, is charged 9 grams of sodium lauryl sulfate and 420 ml. of distilled water. After stirring at room temperature for 1 /2 hours, 1% grams of sodium pyrophosphate, 1 /2 grams of potassium persulfate and 350 cc. vinyl isobutyl ether are added with stirring. Stirring is continued for 1 /2 hours and from an addition funnel a mixture is slowly introduced containing 135 grams polymerization inhibitor-free n-octyl acrylate and 32 grams of inhibitor-free n-butyl acrylate. The time of addition is 1 /2 hours. Temperature of the reaction mixture during reaction is to F.

The total mixture is vigorously stirred at to F. for 4 hours. After heating slowly to R, an exothermic reaction takes place. A cold Water bath is used to cool the reaction mixture. The thickened mixture is stirred at 140 to 150 F. for 4 hours. The resulting polymer is coagulated by the addition of 20 grams of hydrated aluminum sulfate, Al (SO -l8H O. After stirring at 140 F. for 2 hours, the lower layer is decanted. A total of 700 ml. distilled water is added to the reaction flask and stirring is continued for 2 hours at 140 F. The polymer is dissolved in 300 ml. of benzene and reprecipitated with 750 ml. of methanol. The solvents are removed from the reaction mixture by distillation under reduced pressure. The copolymer product obtained after the removal of the solvents is the ternary copolymer of vinyl isobutyl ether, n-butyl acrylate and n-octyl acrylate 2 4.9 having a mole ratio of 1 to 0.25 to 0.75. The copolymer has a molecular weight of approximately 200,000.

The superior properties of the novel vinyl alkyl ether and alkyl ester copolymers according to the invention 4 with the alkyl esters in similar compositions is about 140 and that with vinyl ether is about 130, the viscosity index With the preferred copolymers of the invention is as high as 170, which is surprisingly better than would be expected are illustrated by their remarkable efifect in lubricating 5 from the average of the .two types.

oils as shown by data from a number of tests. In these We claim:

tests, various amounts of the copolymer thickeners are 1. The copolymer of monomers consisting essentially incorporated in the oils as noted in the following table of (A) vinyl alkyl ether having from 4 to 6 carbon atoms in terms of percent by weight and the improvement in the in the alkyl group and (B) a member of the class conviscosity index is observed. 10 sisting of mixed alkyl acrylates and mixed alkyl meth- Oil A is a solvent refined mineral lubricating oil base acrylates having from 4 to 12 carbon atoms in the alkyl containing 45 millimoles per kilogram of basic calcium groups and the total of the number of carbon atoms petroleum sulfonate, 10 millimoles per kilogram of zinc in the alkyl group of (A) and the average number of di(alkylphenyl)diethiophosphate and 0.25% by weight of carbon atoms in the mixed alkyl groups of (B) being diparaffin polysulfide. The viscosity of Oil A at 100 F. 15 from about 8 to about 12, said alkyl groups consisting is 179.5 SSU (Saybolt seconds Universal) and the visentirely of carbon and hydrogen, the mole ratio of (A) cosity at 210 F. is 45.07 SSU giving a viscosity index to (B) being approximately 1:1 and the molecular weight of 96. of the copolymer being at least about 50,000.

Oil B is a solvent refined mineral lubricating oil con- 2. The copolymer of monomers consisting essentially taining 40 millimoles per kilogram Of bflSlC (22116111111 petro- 0f vinylisobutyl ether and (B) a mixture of n-butylleum sulfonate, 6 millimoles per kilogram of Zinc di(alkylacrylate and n-octylacrylate in a monomer ratio of phenyl)dithiophosphate, 0.25% by Weight diparaffin poly- 0.25:0.75, the mole ratio of (A) and (B) monomers sulfide and 0.001% by Weight of silicone foam inhlbltor. being approximately 1:1 and the molecular weight of The base oil has a viscosity index of 96. the copolymer being at least about 50,000.

Oil C is a typical 140 neutral mineral lubrlcating oil. 3. The copolymer of monomers consisting essentially The base oil has a viscosity index of 90. of (A) vinyl-n-butyl ether and (B) a mixture of n-butyl- 011 D 15 3. typ1cal 150 neutral mineral lubricating oil. aerylate and n-octylacrylate in a monomer ratio of The base 011 has a viscosity index of 90. 0.75 :0.25, the mole ratio of (A) and (B) monomers Table 'I 1; 1 P t A Example R1 R2 R5 R4 R5 w it y wfifil- Oil 1 ;1 1: M li l t. V,I.

No. $182+ mer (Thou- 100 F 210 F 9R1 sands) H 1 0. 25 0.75 11 A 3. 385 470.4 80. 139 H 1 0.75 0. 25 9 A 3. 75 200 222.4 70.10 107 H 1 0.75 0. 25 9 A 4 455 201.9 88.9 104 H 1 0.75 0.25 9 B 2 175 191.4 54.8 158 H 1 0.75 0. 25 9 B 3 230 210.9 03. 27 105 H 1 0.75 0. 25 9 B 4 205 220.9 72.47 107 H 1 0. 75 0. 25 9 o 4 300 203.5 71.11 170 1 0.5 0.5 15 B 2 70 210.0 50.33 do 1 0.75 0.25 11.5 B 2 80 203.1 50.55 2-Et. hexyl 1 0.5 0.5 17. B 2 00 213.2 49.75 124 0x0decyl. 1 0.5 0.5 18 B 2 80 219.0 50. 45 120 1 1 12 B 2 244.7 53.10 129 1 1 12 B 2 140 245.4 53.10 129 1 1 12 B 2 175 259 54.89 131 1 0.5 0.5 10 E 4 240 313.0 00.92 142 do 1 0.25 0.75 11 A 4 285 437.4 74.32 130 Z-Et. hexyL- 1 1 12 o 4 480 507 80.83 140 nOctyl 1 0.5 0.5 10 0 4 200 318.4 07. 85 147 1 1 10 B 2 385 304.1 04.14 1 0. 25 0. 75 9 A 4 310 326.8 70.39 154 1 0.4 0.0 9.0 A 4 395 434.7 83.81 140 1 0. 25 0.75 9.5 A 4 295 297.7 74.84 157 Ethyl 1 1 10 A 3. 75 1,225 011 149.5 147 2-Et.l1exyl. 1 1 10 A 3.75 115 308.0 58.18 128 Ethyl 1 1 12 A 3. 75 300 402.5 78.28 138 From the tests in the foregoing table, it will be seen that each of the illustrative compositions containing the copolymeric thickeners according to the invention possesses surprisingly improved viscosity temperature properties compared to base oils alone. Furthermore, the particular copolymers of vinyl alkyl ethers and alkyl methacrylates having the appropriate balance of carbon atoms in the alkyl groups are much superior to other closely related copolymers Without this proper balance.

The above results are even more surprising when compared to viscosity indexes obtained with homopolymers of either vinyl alkyl ether or alkyl acrylates or alkyl methacrylates alone. Although the viscosity index obtained being approximately 1:1 and the molecular weight of the copolymer being at least about 50,000.

References Citedin the file of this patent UNITED STATES PATENTS 

1. THE COPOLYMER OF MONOMERS CONSISTING ESSENTIALLY OF (A) VINYL ALKYL ETHER HAVING FROM 4 TO 6 CARBON ATOMS IN THE ALKYL GROUP AND (B) A MEMBER OF THE CLASS CONSISTING OF MIXED ALKYL ACRYLATES AND MIXED ALKYL METHACRYLATES HAVING FROM 4 TO 12 CARBON ATOMS IN THE ALKYL GROUPS AND THE TOTAL OF THE NUMBER OF C ARBON ATOMS IN THE ALKYL GROUP OF (A) AND THE AVERAGE NUMBER OF CARBON ATOMS IN THE MIXED ALKYL GROUPS OF (B) BEING FROM ABOUT 8 TO ABOUT 12, SAID ALKYL GROUPS CONSISTING ENTIRELY OF CARBON AND HYDROGEN, THE MOLE RATIO OF (A) TO (B) BEING APPROXIMATELY 1:1 AND THE MOLECULAR WEIGHT OF THE COPOLYMER BEING AT LEAST ABOUT 50,000. 